Does the Position of the Third Molar Have an Influence on the Location of Mandibular Fractures?

Julio Cesar C Moretti; Rubens Camino Junior; Celso F Palmieri Jr; Joao Gualberto C Luz

doi:10.4103/denthyp.denthyp_64_22

ORIGINAL RESEARCH

Year : 2022 | Volume : 13 | Issue : 3 | Page : 86-89

Does the Position of the Third Molar Have an Influence on the Location of Mandibular Fractures?

Julio Cesar C Moretti¹, Rubens Camino Junior², Celso F Palmieri Jr³, Joao Gualberto C Luz²
¹ Oral and Maxillofacial Surgery Specialized Center, Paulista Association of Dental Surgeons, São Paulo, Brazil
² Department of Oral and Maxillofacial Surgery, School of Dentistry, University of São Paulo, São Paulo, Brazil
³ Department of Oral and Maxillofacial Surgery, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA

Date of Submission	29-May-2022
Date of Decision	29-Jun-2022
Date of Acceptance	04-Jul-2022
Date of Web Publication	19-Sep-2022

Correspondence Address:
MS,PhD Joao Gualberto C Luz
Department of Oral and Maxillofacial Surgery, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227, Cidade Universitâria, São Paulo
Brazil

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/denthyp.denthyp_64_22

Abstract

Introduction: This study evaluated the possible influence of the lower third molar and its position on the location of fractures in all mandibular regions. Methods: Computed tomography scans of patients with mandibular fractures in any region seen between August 2018 and July 2019 were evaluated. The presence and classification of third molars according to their vertical and horizontal positions and angulations were analyzed. Data were analyzed using the chi-square test, tree algorithm, and random forest model. Results: A total of 49 patients with mandibular fractures were seen and 40 patients (80% men), with a mean age of 33.4 years, were included. There was no correlation between fracture location and the vertical (P = 0.93) and horizontal (P = 0.76) Pell and Gregory classifications. There was a statistically significant relationship between fracture location and the Winter angulation classification (P = 0.01). Conclusion: Relative to the possible influence of lower third molars and their position on the location of mandibular fractures in all mandibular regions, only the angulation of the third molar had an influence. There was no correlation between the presence and the classifications of third molar impaction.

Keywords: Mandibular fractures, random forest model, third molar, tree algorithm, X-ray computed tomography

How to cite this article:
Moretti JC, Camino Junior R, Palmieri Jr CF, Luz JC. Does the Position of the Third Molar Have an Influence on the Location of Mandibular Fractures?. Dent Hypotheses 2022;13:86-9

How to cite this URL:
Moretti JC, Camino Junior R, Palmieri Jr CF, Luz JC. Does the Position of the Third Molar Have an Influence on the Location of Mandibular Fractures?. Dent Hypotheses [serial online] 2022 [cited 2023 Jun 5];13:86-9. Available from: http://www.dentalhypotheses.com/text.asp?2022/13/3/86/356344

Introduction

Mandible fractures are frequent, ranging from 24.3% to 81.3% of the facial trauma cases.^[1],[2] The mandible structure presents areas of fragility, such as the sharp condylar process, the narrow-angle region, and the body that encompasses the mental foramen. The most frequent locations of mandible fractures are in the condylar, angle, body, and symphysis or parasymphysis regions.^[3],[4]

Greater fragility of the angle or condylar regions can be associated with the presence or absence of unerupted third molars.^{[2],[5],[6],[7],[8]} This hypothesis has been supported by finite element analysis studies.^[9],[10] However, in our practice, the frequent presence of third molars in mandible fractures that occur in regions other than the angle has been verified. The location of fractures also depends on trauma factors.^[9]

It has been reported that patients with mandibular third molars have a 2.7 times greater chance of an angle fracture, and the risk for an angle fracture varies depending on the third molar position.^[11] It has been reported that prophylactic removal of lower third molars could increase the risk of condylar fractures.^[12]

The aim of this study was to evaluate the possible influence of the lower third molar and its position, on the location of fractures in all mandibular regions.

Subjects and Methods

A retrospective study was conducted with the medical charts and computed tomography images of patients treated at the Oral and Maxillofacial Surgery Clinic of a Level I Trauma Center. All of the patients who participated in the study signed an informed consent. Patients aged ≥16 years with isolated or combined mandibular fractures in any region seen between August 2018 and July 2019 were included, regardless of their gender and race. Patients with incomplete medical records or unavailable computed tomography images were excluded from the study. This study was approved by the Human Research Ethics Committee of the School of Dentistry, University of São Paulo, Brazil (Protocol no. 626.291).

The presence of the lower third molar, and the Pell and Gregory impaction (vertical and horizontal) and Winter angulation classifications were used.^{[5],[13],[14],[15],[16]}

The fracture location was divided into symphysis (including symphysis and parasymphysis fractures), body, angle (including angle and ramus fractures), condyle, coronoid process, and alveolar process.

The chi-square test was used to verify possible relationships between the fracture location and the Pell and Gregory horizontal/vertical, and the Winter classifications, using SPSS 24.0 (IBM, Chicago, IL). Also, tree algorithm and random forest model (a machine learning algorithm) were employed to analyze the data using the Python 3.10.4 (The Python Software Foundation, https://www.python.org) and R 4.1.3 (R Foundation for Statistical Computing, Vienna, Austria).

Results

During the study period, 49 patients with mandibular fractures were assessed and 40 patients with third molar were included (age: 33.4 ± 11.9 years; 80% male). Descriptive data related to fracture location and impaction classification are shown in a dataset supplementary file. (Moretti JCM. Fracture and impaction features. Figshare. Journal contribution. 2022. https://doi.org/10.6084/m9.figshare.20161343.v1).

There was no correlation between fracture location and the vertical (P = 0.93) and horizontal (P = 0.76) Pell and Gregory classifications. There was a statistically significant relationship between fracture location and the Winter angulation classification (P = 0.01). Results of tree algorithm and random forest model are shown in [Figure 1] and [Figure 2].

Figure 1 Results of tree algorithm that splits the data into nodes by class purity. More complex tree included age as another variable is presented in a supplementary file. (Moretti JCM. Fracture and impaction features. Figshare. Journal contribution. 2022. https://doi.org/10.6084/m9.figshare.20161343.v1).

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Figure 2 Results of the random forest model (a machine learning algorithm; number of trees: 500) showing variable importance and ROC curve of out of bag (OOB) score.

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Discussion

This study evaluated the influence of the presence of the lower third molar and its position on the location of fractures in all mandibular regions. There was no correlation between the presence of the third molar and the classifications of third molar impaction. There was a significant difference only in the angulation classification of the third molar and the fracture location. These results differed from those of studies on the location of mandible fractures in the specific regions of the condyle and angle relative to the presence or absence of third molars.^[6],[9] Examples of findings are shown in Figures 3 and 4 supplementary file. (Moretti JCM. Computed tomography examples. Figshare. Journal contribution. 2022. https://doi.org/10.6084/m9.figshare.20161454.v2).

One of the limitations of this study stems from the fact that other factors that may influence the location of mandible fractures were not analyzed, such as the intensity and direction of the impact and the shape of the object causing the impact, as well as the position of the mandible and the influence of associated soft tissues, such as fascial and periosteal attachments.^{[2],[9],[17],[18]} However, such data are difficult to obtain with trauma victims.

There was a predominance of the third molar ipsilateral to the mandible fracture. However, when considering the presence of the third molar with the location of the fracture, there was no significant difference. When an applied force is sufficient to result in a mandible fracture and a third molar is present, the fracture is more often in the angle region.^[7],[13] However, angle fractures depend on other factors such as the force vector, trauma intensity, facial musculature, and mandibular architecture.^[18] These differences in results are likely to be the result of most studies which only assessed condylar and angle fractures, while our study included all locations of mandible fractures.

According to the Pell and Gregory classification, horizontal and vertical, it has been reported that patients with erupted third molars are twice as likely to have condylar fractures compared to patients with impacted third molars.^[4] A direct relationship between the position of the third molar and the greater number of angle fractures or the absence of the third molar and the greater frequency of condylar fractures would be due to the presence of the superficially impacted third molar which weakens the mandibular angle due to the discontinuity of the cortical bone.^[18] However, there was no significant difference in the cases evaluated in our study. It has been described that with a front blow, irrespective of the third molars, the mandibular condyle, rather than the angle of the mandible, has a higher risk of fracturing.^[10]

It was observed that most third molars related to mandibular fractures were in the vertical or mesioangular position, considering the Winter classification. There was a statistically significant difference when comparing the angulation classification with the location of the fracture. Initially, the presence of the third molar in these positions seems to play an important role in the greater number of angle fractures, due to the interruption of the cortical bone and the wedge effect caused by the dissipation of the kinetic energy of trauma by the root of the third molar.^[19] However, our study showed that there was a third molar present in the vertical and mesioangular positions, not only in angle fractures but also in condylar fractures, contradicting the theory presented.

The lack of standardization in the study designs, as well as the heterogeneity of the samples, seem to be important factors that have contributed to the variety of results.^[20] More research is required to correctly examine the direction and magnitude of the external force application, the quality of the bone of the mandible, and the correlation between these factors and the mandible angle and condylar fractures.^[12] The fracture risk could be predicted using anatomic features, such as the retromolar space, perimeter of the cross-section proximal to the second molar, breadth of the ramal cross-section, the thickness of the oblique ridge, gonial angle, and location of the ipsilateral mental foramen.^[20]

Conclusion

It was concluded that only the angulation of the third molar had an influence on the location of mandibular fractures. There was no correlation between the presence of the third molar and the classifications of third molar impaction. Furthermore, there was no influence of personal data or etiology on the location of mandibular fractures.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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